Electric furnace



Feb. 7, 192s. 1,658,651

R. B. PRINDLE ELECTRI C FURNAC E Filed Dec. 29. 1925 lllllllll l RamondB. Prindle;

His Atmorneg.

Patented Feb. 7, 1928.

UNITED STATES PATENT OFFICE.

RAYMOND B. PBINDLE, 0I' SCHEHECTADY, NEW YORK, ASSIGNOR T0 GENERAL ELEC-TBIC COMPANY, A CORPORATION 0F NEW YORK.

ELECTRIC 'FURNACE Application filed JDecember 29, 1986. Serial No.157,816.

My invention relates to electric furnaces and has for its object theprovision of simple and reliable means for sealing a furnace receptaclearound an electrical conductor passinv through the wall thereof,

ore particuularly my invention relates to electrical apparatus, such aselectric fur- Cil naces, and the like, in which a sealed chamber isused, such for example as a vacuum furnace, in which the air isevacuated from the heating chamber. In such furnaces, it is customary toplace the electric heater in the evacuated heating chamber, and myinvention in one of its applications relates to means for sealing thechamber around the electrical terniinals or leads for the heater.

In carrying out my invention I provide a seal including an annularmember made of a suitable vitreous material, such as glass. This memberis sealed in the opening for the terminal lead and electricallyinsuluates the terminal as well as facilitating the formation of a seal.

For a more complete understanding of my invention reference should behad to the accompanying drawing in which Fig. 1 is a fragmentarysectional view of a seal for electric furnaces embodying my invention,While Fig. 2 is a fragmentary sectional view to a reduced scale showingan electric furnace embodying my invention.

Referring to the drawing, I have shown my invention in one form asapplied to a vacuum furnace of the type shown in Patent No. 1,566,224 toMassey, although obviously my invention has application to various othertypes of furnaces. Briefly, this furnace comprises a cylindrical casingor tank 10 forming a heating chamber and provided with a cover 11. Thiscasing is made of a non-porous material of sufficient strength to permitthe air to be evacuted, such for example as steel. Inside the casing isan electric heating resistor 12 shown in the form of a wire wound in ahelix on a cylindrical support 13 made of a suitable heat refractory,electrically insulating material, such as alundum. Between the heatingresistor and the casing 10 is a cylindrical heat refractory insulatingmember 14 which also may be made of alundum. To facilitate cooling, thecasing 10 is placed in a large t-ank 15 which is filled with water tocover the casing 10. The cooling water is preferably admitted at thebottom of the tank through 'a pipe, not shown an overflow pipe 16 beingprovided to limit the water level.

A downwardly projecting flange 17 is provided around the periphery ofthe cover 11. This flange projects into a trough-like receptacle 18secured to the casing 10 at the top thereof. A quantity of metal 19 oflow melting point, such for example as solder, is provided in thereceptacle 18. The flange 17 is embedded in the solder and a tight sealthereby formed between the cover and the casing. A suitable electricheating unit 20 is provided in the receptacle whereby the solder may bemelted to permit the cover to be put in place and removed.

As shown, the terminal leads 21 and 22 for the heating resistor arebrought out through the cover 11, a suitable air-tight seal beingprovided for each terminal` The construction of the seal isshown indetail in liig. 1. It comprises a metallic sleeve 23 which is tightlysecured at its lower end by means of a welded or similar joint in anaperture in the. cover 11. The upper end of the sleeve is reduced indiameter as compared with the lower end so as to form an enlarged baseportion 24. Secured to the upper end of the sleeve 23 is a sleeve 25made of a suitable vitreous insulating material, such as glass. Theupper end of the sleeve 25 in turn is closed by a metallic cap member 26which serves as a support for the terminal lead 27 extending centrallythrough the sleeves 23 and 25 into the furnace chamber. The sleeve 23and the cap 26 are made of a suitable metal having a temperaturecoefficient of expansion similar to that of the glass sleeve 25 and asurface oxide which combines readily with the glass. This materlal, forexample, may be copper, invar or chrome-steel. The terminal lead 27 isshown as a solid rod made of a suitable electrically conductingmaterial, such as copper, although it may be flexible. A lava spacinginsulator 28 is provided inthe lower end of the sleeve 23 to preventlateral displacement loov of the terminal lead 27 and resultant break- Istranded material 'and are of suiiicient length to allow the cover to betilted upward to give access to the interior of the 'heating' chamber.

The glass sleeve 1s enclosed and protected from mechanical injury bymeans of a sleeve 29 made of a suitable flexible electrically insulatingmaterial, su'ch as fibre. This sleeve has a slot extending throughoutits length, as indicated by the numeral 30, so that it may besli pedover the enlarged base portion 24 of t e metallic sleeve and contractedand secured tightl thereon by means of a clam 31. The g ass sleeve 25and the cap memlber 26 are both smaller in diameter than the baseportion 24 and are consequently spaced from the sleeve 29 y Serve whichthus forms an eiiicieiit guard for these parte A iiexible lead 32extends from the u per end Aof the cap 26 to the clamp 31 wlere it issecured to a connection lug 33 by means of a suitable bolt 34. Thislconstruction prevents breakage of the glass sleeve 25 by a pull whichmight otherwise.

bev ap lied to the lead'32. lIt will be obdp that all strains set upinthe external electrical connections for the furnace are taken upby theprotecting sleeve 30.

While I'have described my invention as embodied in concrete form and asoperating in a specific manner in accordance with the provisions of thepatent statutes, it should be understood that I ,do not llimit myinvention thereto sinceA various modifications thereof f will suggestthemselves to those skilled in the art without departing' from thespirit of my invention the scope ofwhich is set forth in the annexedclaims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

' 1. An electric furnace com rising a' receptacle forming a heating camber, said receptacle being provided with an opening,"

an electric heater in said chamber, a terminal lead fof said heaterextending through said opening, and means for sealin said receptaclearound said terminal lea includ-v ing an insulating vitreous sleeve,said sleeve bein combined at its ends with said termina v sealed jointstherewith.l

2. An electric furnace com rising a re'- ceptacle forming a'. heating camber, said receptacle being providedwith an opening,

an electric heater in said chamber, a terminal lead for said lheaterextending through said opening, and means for sealing -said receptaclearound said terminal lead including an annular glass member, said glassmember being combined at its ends with said terminal lead and saidreceptacle to f form sealed joints therewith.

3. An electric furnace comprising a ren 1of an electric h `a. terminallead for lead 'and said receptacle Ito forml ceptacle forminga vacuumheating chamber, an electric heater in said chamber, anA

sleeve secured to said metallic sleeve, and a` said termetallicsupporting member for minal secured to said glass sleeve.

I 5. The combination with a receptacle pro vided with an opening, of anelectrical conductor extending through'said opening, an

annular3 glass member secured to said re- Ceptacle around saidconductor, a metallic member secured to .said glass member forming asupport for said conductor, an outer protecting member surrounding saidvglass member, and an electrical conductor having One end secured to saidmetallic member and its other end carried by said protecting member.'

6. TheJ combination with a receptacle provided with anopening, of anelectrical conductor extending throu h said opening, a

metallic member secure to said receptacle in said opening, a glassmember secured to said metallic member, a metallic cap member secured tosaid glass member, an electrical connection between Asaid conductor andsaid cap member, an outer protecting member .of insulating material, aclamping member securing said protecting member to said metallic member,and an electrical conductor secured 'to said cap member and ,saidclamping member. n

7 The combination with a receptacle provided with an opening, of anelectrical conductor extending' through said opening, a

metallic sleeve secured to said receptacle in said openings, a glasssleeve secured to said metallic sleeve, a metallic cap member se# curedto said glass sleeve, an electrical connection between said conductorand said cap member, an outer protecting member of in sulatingmaterialsurrounding said sleeves. a clamping member securing saidprotecting member to said metallic sleeve, and an electrical conductorsecured to said cap member and said clamping member.

In witness whereof, I have hereunto set my hand this 28th day ofDecember, 1926. RAYMOND B. PRINDLE.'

